Electric control circuits



Jan. 25, 1949. E. M. GARDINE R EfAL, 2,460,127

ELECTRIC CONTROL. CiRCUITS Filed July 2, 1946 I lnven'tohsz Edward M.Gar*dine-r-,

Orffin W. Livingston,

OYM HM Their Attor hey.

Patented Jan. 25, 1949 ELECTRIC, CONTKQL CIRCUITS Edward M. Gardiner, Schcncctady; -and. .Onrin'=W;

Livingston, "Scotia. JN; :'.,.;assi gnors to General. Electric Gompanpacomorationof New York Application m 2, 194e,;semrm. 680,962

Our invention relates to electriccontrol oilcuits and more particularly to an improved control circuit for effecting the closing and opening of an alternating current circuit during-cycles of voltage of predetermined polarity.

While not limited thereto, we have applied our invention successfully to a testing circuit for electr c discharge devices of the gas or vaporfilled type in which the anode-cathode circuit of the device to be tested is established for. half cycle or predetermined number of half cycles by closure of an electromagnetic switching device connected in series with the anodecathode circuit and controlled synchronously. with the voltage of the alternating current supply so that all operations of the switching device are accomplished during half cycles of neg-ative voltage of the supply circuit.

It is an object of our invention toprovldea new and improved electric circuit.

It is another object of our invention 'toprovide a new and improved switching circuit.

It a still further object of our invention to provide a new and improved electric control circuit particularly adapted for establishing" a circuit including a unilaterally conductive device and a source of alternatingvoltage-during half cycles of the voltage during 'wl'iich th'esunilateral device is nonconductive.

Further objects and advantages of our inveni will become apparent as the following-description proceeds, reference being had to 'the accompanying drawing, and its scope will. be pointed out in the appended claims. In the drawing, the single figure is a schematic repree sentation of a tube testing circuit embodying our invention.

Referring now to the drawing; we haveushown our invention embodied in a controhcircuiti'rfor measuring the arc drop of an electric discharge" device 5 during predetermined half :cycles of the normally open. contacts -oi an electromagnetic relay H and oneeof a plural'ityroif r esisters M which are selectivelyeonnectetleinuthe 30la'ims. (chars-cm) during: a negative half cycle of the supply cir chit:'voltageyand'to maintain the circuit closed -inzithe -drawing, the transformer 28 alsoincludes vihalf- :cycle of voltage. r-accomplis-h'ing this end is in the nature of a circuit by-aswitch. it. The cathode of the device==l isconnec'ted with the other side of the alternating current circuit by conductor l8 and manual switch i1; As illustrated, the switch 1 l maybe moved to engagement with a contact Hicon-nected with the midpoint of the secondary win-ding t9 of a filament transformer for the purpose-of completing the anode-cathode circuit for devices designed to operate with the cathode circuit-established through the midpoint of. the secondary winding of the heatersupply transformer; As illustrated, the end terminals of the transformer secondary winding Iii are connected withtthei'heater element 5. The primary windlng lll offtransformer 20 is energized from the alternating current supply circuit 2 by means of anauto-transformer '22 having an adjustable tap523. A voltmeter 24 may be connected across theiheatercircuit for use in adjusting the heater voltage to rated. value.

In accordance with an important feature of our invention, the relay H is energized synchronously with respect to th voltage of the alternating current supply circuit 2 to close the anode-cathode circuit of the discharge device l llorrioneor more positive half cycles of this voltage, and to open the circuit during a negative The control circuit for single-tube inverter and is energized from a suitable'i'source of direct current voltage including :c'onductorsv25 and 25 which may to advantage :be energized from the output of a rectifier circult connected between the alternating current .su'pply circuit 2 and the conductors 25 and 26.

. Asiillustrated, this circuit includes the secondary winding zlwof" a transformer 28- having the prh mary winding 29' thereof energized from the alternating current supply circuit 2 and a full -wave:.-el'ectricdischarge device 38. A suitable current limiting resistor 38 is connected between the transformer winding 2? and the anode cathode-circuits of the-device-iell; As illustrated :ahsecondary, winding 32 for supplying heating icurrent tothe cathodes of the discharge device iinnnd a ifurth'er winding 33 for energizing. the

cathode' iheater. of an electric discharge device :Skwhich; ,asswill,beiidescribed laterv in the specifiiiormsz-a part of a measuring circuit-for indicating --the peak voltage drop across the ;anod:e;-.cathode.-circuit;.of the discharge device! mmierrtest. 1

The direct current voltage provided by conductors and 2B is filtered by a shunt capacitor and impressed on a series circuit including a normally open push button switch 35, capacitors 31 connected in parallel and a charging resistor 38. It will be apparent that the capacitors 3'! charge from the direct current voltage of conductors 25 and 28 upon closure of the switch 36 at a rate dependent upon the magnitude of the charging resistor 38. The circuit including switch 36 and capacitors 31 is shunted by a series circuit in cluding a resistor 39, an operating coil 40 of the relay H, and the anode-cathode circuit of an I the conducting half cycle of device I.

electric discharge device 4| which may to advantage be of the gas-filled type. This latter circuit including the discharge device 4i controls the discharge of capacitors 3! and the duration of each period of energization of the operating coil 40 of the relay II. In order to synchronize the initiation of conduction by electric valve 4| with the voltage of the alternating current supply circuit 2, the circuit of the control member thereof is completed from the cathode of the device, through resistor 38 which provides a negative bias having a magnitude dependent upon the condition of charge of capacitors 31, and the secondary winding 42 of a peaking transformer 43 having the primary winding 44 thereofenergized from the alternating current supply circuit 2. The secondary winding 42 is connected with proper polarity so that the voltage peaks tending to render the control member of valve 4i positive with respect to the cathode occur during half cycles of the supply circuit voltage during which the anode 3 of discharge device I is negative. The circuit or the control member of valve 4! also includes a series current limiting grid resistor 45 and a shunt transient suppressingcapacitor 45 in accordance with practice Well established in the art.

The conductors 25 and 26 also provide a source of direct current voltage for a peak voltage measuring circuit for indicating the voltage drop across the anode-cathode circuit of the discharge device I which is undergoing test.

The voltage,

The anode-cathode circuit of device 34 is completed from the anode of the device, to the conductor 25, through an electric discharge device 62 which may be an indicating tube such as a neon lamp, a current limiting resistor 83 and a resetting push button switch '64 which is, as illustrated, normally biased to the closed position.

of conductors 25 and 2B is regulated by a circuit including a series resistor 41 and a glow discharge device 48 of the type having a critical minimum ionizing potential connected in series across these conductors. The constant voltage appearing across the terminals of the discharge device 48 is impressed on a circuit including, in series, the resistor-s 4952. Resistors 49 and 52 are provided, respectively, with adjustable taps 53 which are arranged to short out variable portions of re- 1 sisters 49 and 52 and which arernechanically interlocked, as indicated at 54, so that as resistor 49 is shorted out, resistor 52 is inserted, so that the total resistance of the circuit including resistors 4952, inclusive, remains constant. The adjustment of the contacts 53 is, therefore, effective to adjust the direct current voltage level of any point upon the resistors connected between these contacts 53. The cathode 55 of the electric discharge device 34 is connected to an adjustable contact 56 on the resistor 5| to establish a reference voltage with which the arc drop voltage of discharge device I is compared as a result of the connection between the grid circuit of device 34 and the anode cathode circuit of'device I. As illustrated, a voltage dividing circuit including resistors 51 and 58 is connected across the anode-cathode circuit 'of device l and the control grid 59 of discharge device-34 connected with the common point of these resistors through" A brief description of the operation of the system described above will serve to emphasize the features and advantages of our invention as well as to point out the manner in which the quality of the discharge device under test is determined. It should be indicated here that the test is D ticularly designed to determine the adequacy of the emission from the cathode of the device I. With the switch I! in the position illustrated in the drawing, the system is energized by closing a line switch, designated by numeral 55. After a brief interval, the cathodes of electric discharge devices I, 30, 34 and 4| are at proper operating temperature and the system is ready for operation. It will be noted that the control members of discharge device I are connected with the anode so that the device will conduct for the full positive half cycle of the supply circuit voltage. The switch i5 is moved to include that one of the resistors I4 in the anode-cathode circuit having the proper magnitude for limiting the discharge current to the desired value. When it is desired to close the relay H, push button switch 36 is closed and capacitors 31 charged from the direct current voltage conductors 25 and 25 through resistor 21. As the capacitors become charged, the negative biasing voltage of resistor 38 decreases in accordance with the decrease in charging current and after a short interval, determined by the charging rate of capacitors 31, the positive voltage peak produced by transformer 42 renders electric discharge device 4| conductive to discharge capacitors 31 through device 4|, the relay coil 40 and the resistor 39. As previously stated, the transformer winding 42 is poled in such a manner that conduction of current occurs during a negative half cycle of the anode voltage of discharge device I, so that when contacts ID are closed no current flows immediately. The period during which the relay remains closed is determined by the constants of the circuit including capacitors 31 of discharge device 41, relay coil 40 and resistor 39. For purposes of the present application, the relay is maintained closed for one cycle so that it opens againduring the next negative half cycle of the supply circuit voltage, after which it is closed to maintain the anode-cathode circuit of the device under test established for one positive half cycle. The resistor 39 is included so that the damping of the relay circuit is controlled to minimize bouncing of the contacts of the relay II.

It will be apparent that during the next positive half cycle of voltage of the supply circuit 2- after the contacts of relay .l l are closed the electric discharge device I will conduct current and the-voltage whichv appears across the anode-cathode circuit of the device will be dependent upon, among other things, the emission of the cathode 4. This voltage is impressed on the control member 59 of discharge device 34 and, as a result of the connection of the cathode with a suitable point on resistor 5|, is compared with the regulated voltage appearing between the tap on resistor 52 and the contact 56 of resistor 5|. If the voltage impressed on control member 59 of valve 34- exceeds a predetermined magnitude determined by the voltage of the tap 56, valve 34 conducts to ignite the indicating lamp 62 and in this way indicates excessive arc drop in the device under test as the result of inadequate emission from the cathode. voltage indicating circuit may be reset by opening the push button switch 64. It will also be apparent that the adjustable contacts 53 and 56 provide an arrangement for adjusting the operation of the voltage measuring electric valve 34 to render the indicating lamp 62 conducting on the occurrence of a predetermined arc-drop across the device. As previously mentioned, the capacitor 6| is included in the circuit of control member 59 for the purpose of by-passing the initial steep wave front voltage occurring upon establishment of conduction in discharge device 5. This is necessary since this first voltage is not indicative of the adequacy of emission from the cathode, and it is the subsequent peak arc discharge voltage which it is desired to measure.

For purposes of the present invention, it is desired to maintain the anode-cathode circuit of the device closed for only one-half cycle at a time since under this condition heating of the cathode due to the arc current is negligible. The are drop is then determined by the electron emission of the cathode at the operating temperature produced by the heater when energized with normal heater voltage. It will be apparent that by adjustment of the constants of the circuit including discharge device M, the relay ll may be maintained closed for different periods of time. By utilizing a circuit which opens and closes the relay contacts during negative half cycles of voltage of anode 3 of device I, the contacts of the relay are relieved of all current making and breaking functions. Thus the relay H may be of small current interrupting capacity.

While We have shown and described a particular embodiment of our invention, it will be apparent to those skilled in the art that changes and modifications may be made without departing from the features of our invention, and we, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, an alternating current supply circuit, a unilaterally conducting device, an electromagnetic switching device having a contact connecting said device to said alternating current circuit for energization therefrom, elec- It will be understood that the tric valve timing means including peaked voltage producing means for initiating operation of said timing means, means impressing a voltage derived from said alternating current circuit on said timing means to effect operation of said switching device during half cycles of voltage of said supply circuit during which said device is nonconductive as a result of its unilaterally conductive characteristic, a capacitor, and a circuit completed by operation of said peaked voltage producing means for efiecting operation of said switching device to open position a predetermined time after circuit closing operation thereof.

2. In combination, an alternating current supply circuit, an electric discharge device including an anode, a cathode, an electromagnetic switching device having a normally open contact connecting the anode-cathode circuit of said discharge device to said alternating current circuit for energization therefrom, timing means, means for deriving a voltage from said alternating current circuit and impressing it on said timing means to effect closing and opening operation of said switching device during half cycles of voltage of said supply circuit which are negative with respect to the anode of said electric discharge device, and means connected to respond to the anode-cathode voltage of said discharge device to measure the arc drop voltage of said discharge device during conduction.

3. In combination, an alternating current supply circuit, an electric discharge device including an anode, a cathode, an electromagnetic switching device having a contact connecting the anodecathode circuit of said discharge device to said alternating current circuit for energization therefrom, timing means, means for deriving a voltage from said alternating current circuit and impressing it on said timing means to effect closing and opening operation of said switching device during half cycles of voltage of said supply circuit which are negative with respect to the anode of said electric discharge device, means for establishing a present voltage and means including an electric discharge device connected to said last-mentioned means and to the anode-cathode circuit of said device for comparing the arc drop voltage of said device with a preset voltage.

EDWARD M. GARDINER. ORRIN W. LIVINGSTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,010,697 Lord Aug. 6, 1935 2,366,984 Scheg et al Jan. 9, 1945 2,366,988 Rees Jan. 9, 1945 2,424,329 Penney July 22, 1947 

